Cushion body, seat, and method of manufacturing the same

ABSTRACT

A cushion body, which can secure both soft touch feeling and durability, a seat having the same, and a manufacturing method thereof are provided. 
     A cushion body  11  is constituted by stacking a sheet-like fibrous structure  4   a  with a low density in which webs  2  are stacked such that their extending direction conforms with a thickness direction T of the cushion body and a sheet-like fibrous structure  4   b  with a high density whose flexing degree to load in the thickness direction T is smaller than that of the sheet-like fibrous structure  4   a  with a low density, where the sheet-like fibrous structure  4   a  with a low density is disposed nearer a sitting surface  10   a  than the sheet-like fibrous structure  4   b  with a high density. Since the sheet-like fibrous structure  4   a  with a low density on the side of the sitting surface  10   a  receives load from the outside of the cushion body  11  due to sitting and flexes largely, it provides soft touch feeling to an sitting occupant. On the other hand, since the sheet-like fibrous structure  4   b  with a high density is small in flexing amount and it has hardness to some extent, it is hard to fatigue in a load direction, so that durability can be secured.

TECHNICAL FIELD

The present invention relates to a cushion body, a seat, and a method of manufacturing the same, and in particular to a cushion body and a seat using a fibrous structure composed of polyester fibers or the like, and a method of manufacturing the same.

BACKGROUND ART

Conventionally, a seat using a fibrous structure composed of polyester fibers or the like as a cushion body has been known (for example, see Patent Document 1).

The fibrous structure used in the seat described in Patent Document 1 is formed by successively folding a web obtained by dispersing and incorporating thermally adhesive composite short fibers as adhesive component into matrix fibers composed of an inelastic polyester crimped short fiber assembly in a standing state along its longitudinal direction. That is, this fibrous structure is formed to have a predetermined thickness by folding the web in an accordion shape.

In the seat described in Patent Document 1, each of a seat portion and a seat back portion is constituted by stacking a plurality of this fibrous structures to form a cushion body and coating this cushion body with a cover. Accordingly, in this seat, since the standing direction of the web (a thickness direction of the cushion body) is directed along a load direction during sitting of a seat occupant, excellent ventilation is, of course, secured, a proper hardness to a load direction is provided, and load can be dispersed. Therefore, this seat can provide soft touch feeling which cannot be obtained by urethane conventionally used in general.

Patent Document 1: Japanese Patent Laid Open Publication No. 1996(H08)-318066

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

Since the seat described in Patent Document 1 has a structure that a longitudinal direction of fibers extends along a load direction, it can support a sufficient load while maintaining soft touch feeling.

However, in the seat described in Patent Document 1, since each of the seat portion and the seat back portion is formed by only stacking a plurality of accordion-shaped fibrous structures, soft touch feeling can be obtained but there is a problem that durability is poor as a seat.

On the other hand, when the number of stacks of fibrous structures is increased in order to improve the durability, hardness can be obtained to some extent, but such a drawback arises that unique soft touch feeling of the fibrous structures is lost from the fibrous structures.

An object of the present invention is to provide a cushion body and a seat which can secure both soft touch feeling and durability by stacking a plurality of fibrous structures with a predetermined thickness folded in a standing state, a method of manufacturing the same.

Means for Solving the Problem

A cushion body of the present invention is a cushion body obtained by molding a fibrous structure obtained by mixing main fibers and binder fibers using a mold having a cavity with a predetermined shape, wherein the cushion body is formed by stacking a plurality of the fibrous structures, the plurality of the fibrous structures stacked includes a first fibrous structure and a second fibrous structure which is smaller in flexing degree to load in a thickness direction than the first fibrous structure, the first fibrous structure is disposed nearer a load receiving face of the cushion body on which external load is applied than the second fibrous structure.

Thus, since the first fibrous structure with larger flexing degree is disposed on the side of the load receiving face on which external load is applied in the cushion body of the present invention, the cushion body flexes largely in a load direction when it is applied with external load due to seating or the like. Therefore, soft touch feeling can be provided to a seat occupant during sitting.

Since the second fibrous structure is smaller in flexing degree to load in the thickness direction than the first fibrous structure, it has hardness to a certain extent, so that even if load is applied to the first fibrous structure in the thickness direction, the second fibrous structure can support and disperse the load. Accordingly, fatigue in the load direction hardly occurs in the cushion body so that durability of the cushion body can be secured.

Thus, according to the cushion body of the present invention, both soft touch feeling and durability can be realized.

It is preferable that the first fibrous structure is formed from approximately the same fiber material as the second fibrous structure and is formed to have a fiber density lower than that of the second fibrous structure.

In this case, it is preferable that the first fibrous structure has a fiber density of 10 to 20 kg/m³ and the second fibrous structure has a fiber density of 20 to 35 kg/m³.

Thus, the first fibrous structure and the second fibrous structure are formed from approximately the same fiber material and they are made different in fiber density, so that both the structures can be constituted to have different flexing degrees.

Since the first fibrous structure and the second fibrous structure are formed from approximately the same fiber material, it is unnecessary to separate the fibrous structures into respective different fiber materials at disposal of the cushion body so that work for separation is omitted, which results in improvement of recycling easiness.

Further, it is preferable that the first fibrous structure and the second fibrous structure are applied with different colors or patterns regarding appearances thereof so that both the fibrous structures can be discriminated from each other.

Thus, since the first fibrous structure and the second fibrous structure can be discriminated from each other based upon their different appearance colors or patterns, the fibrous structures can be confirmed and discriminated with eyes. The respective fibrous structures can be disposed at proper positions where they should be disposed. Accordingly, an erroneous combination during manufacture of cushion body can be reliably prevented.

The seat of the present invention is a seat including a cushion body and a seat frame supporting the cushion body, wherein the cushion body is either one of the cushion bodies described above.

Thus, since the seat of the present invention uses the cushion body provided with soft touch feeling and durability such as described above, it is provided with soft touch feeling during sitting on the seat and high durability to load due to sitting on the seat.

The method of manufacturing a cushion body according to the present invention is a method of manufacturing a cushion body comprising a fibrous structure, comprising at least: a fibrous structure forming step of successively folding a web composed of main fibers and binder fibers for each predetermined length to form a fibrous structure as a stacked state; a fibrous structure disposing step of disposing a first fibrous structure of the first structural body and a second fibrous structure included in the fibrous structure nearer a load receiving face of the cushion body than the second fibrous structure and disposing the first and second fibrous structures in a mold having a cavity with a predetermined shape in a stacked and compressed state of the first and second fibrous structures, where the second fibrous structure is smaller in flexing degree to load in a thickness direction than the first fibrous structure; and a molding step of thermally molding the fibrous structure in the mold to form a cushion body.

Thus, in the method of manufacturing a cushion body according to the present invention, since the first fibrous structure and the second fibrous structure are disposed in a state that they are stacked and compressed in the mold and be thermally molded, integral molding can be preformed in the mold. Therefore, a bonding step can be skipped unlike a case that the first fibrous structure and the second fibrous structure are bonded to each other using adhesive, so that tact time spent for cushion body manufacture can be reduced.

In this case, in the molding step, it is preferable that steam is blown to the fibrous structure through steam holes formed on a mold face of the mold under barometrical pressure higher than atmospheric pressure.

Thus, in the method of manufacturing a cushion body, the fibrous structures are disposed in the molding formed with steam holes in a compressed state thereof, and steam is blown to the fibrous structure under barometrical pressure higher than atmospheric pressure. Thereby, steam blown to the mold can pass through the inside of the fibrous structures through the steam holes formed in the mold without causing adiabatic expansion while it is being kept at a molding temperature. At this time, since steam has heat capacity larger than hot air, the fibrous structure can be molded in a short time so that a molding time can be reduced largely in the present invention. Since the molding time is reduced, heating process time of the fibrous structure is reduced, so that texture of the cushion body after molded can be made good.

Furthermore, in this case, it is preferable that the steam holes are formed to be more in a region corresponding to the side of a non-load receiving face where the second fibrous structure is disposed than in a region corresponding to the load receiving face in the mold, and steam is blown to the fibrous structure through the steam holes on the side of the non-load receiving face in the molding step.

Thus, in the method of manufacturing a cushion body according to the present invention, since the number of steam holes on the side of the load receiving face on the mold is larger than that on the side of the non-load receiving face, an amount of steam introduced from the side of the non-load receiving face into the mold becomes more than that introduced from the load receiving face. When the amount of steam introduced is increased, the number of fibers melded and fixed by thermal molding increases so that a structure of the fibrous structure is made firm and hardness thereof is increased. Therefore, hardness of a surface layer of the second fibrous structure disposed on the side of the non-load receiving face becomes harder than that of a surface layer of the first fibrous structure disposed on the load receiving face. That is, it is possible to increase a flexing degree, to a load, of the load receiving face side receiving load from the outside and decrease a flexing degree, to a load, of the non-load receiving face side.

Accordingly, it is made possible to provide a cushion body having both soft touch feeling during sitting on a seat and durability to load due to sitting on the seat.

A method of manufacturing a seat according to the present invention is a method of manufacturing a seat comprising a cushion body and a seat frame supporting the cushion body, comprising at least: a step of forming the cushion body according to the manufacturing method of the cushion body described above; and a step of attaching the cushion body to the seat frame.

Thus, since a cushion body having both soft touch feeling and durability is used as mentioned above, the method of manufacturing a seat according to the present invention can provide a seat having both soft touch feeling during sitting on the seat and durability to load applied during sitting on the seat.

EFFECT OF THE INVENTION

According to the present invention, since the first fibrous structure with large flexing degree is disposed on the side of the load receiving face which is applied with load from the outside, the cushion body flexes sufficiently and largely when it is applied with load from the outside of the cushion body due to sitting or the like. Since the flexing degree of the second fibrous structure to load acting in a thickness direction is smaller than that of the first fibrous structure, it holds certain hardness, so that even if load applied to the cushion body in the thickness direction, the cushion can support the load. Accordingly, both soft touch feeling and durability can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view of a seat.

FIG. 2 is an explanatory diagram of a fiber direction of a web.

FIG. 3 is an explanatory diagram of a manufacturing step of a sheet-like fibrous structure.

FIG. 4 is an explanatory diagram of the sheet-like fibrous structure before stacked.

FIG. 5 is an explanatory view of a mold.

FIG. 6 is an explanatory diagram of a manufacturing step of a cushion body.

FIG. 7 is an explanatory diagram of a manufacturing step of the cushion body.

FIG. 8 is a sectional explanatory diagram of the cushion body.

FIG. 9 is sectional views showing a state that a seat portion of the seat has been cut in a widthwise direction thereof.

EXPLANATION OF REFERENCE NUMERALS

-   1: seat -   2: web -   4 a: sheet-like fibrous structure with a low density (first fibrous     structure) -   4 b: sheet-like fibrous structure with a high density (second     fibrous structure) -   4 c: U-shaped sheet-like fibrous structure -   4 d: protrusion type sheet-like fibrous structure -   10: seat portion -   10 a: sitting surface (load receiving face) -   10 b: back surface (non-load receiving face) -   11, 21: cushion body -   13, 23: cover -   15, 25: seat frame -   17: trim cord -   19: engagement portion -   20: seat back portion -   40: mold -   40 a: cavity -   41: first mold -   42: second mold -   43: steam hole -   50: high pressure steam molding machine -   61: driving roller -   62: hot air suction type heat treating machine -   a: fiber constituting web -   b: lengthwise direction of web -   c: fiber direction constituting web -   θ: angle of lengthwise direction of fiber to lengthwise direction of     web

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the present invention will be explained below with reference to the drawings. Incidentally, parts, arrangements or the like explained below do not limits to the present invention, and the present invention can be modified variously within the scope and spirit of the present invention.

FIG. 1 to FIG. 8 show an embodiment of the present invention, FIG. 1 being an explanatory diagram of a seat, FIG. 2 being an explanatory diagram of a fiber direction in a web, FIG. 3 being an explanatory diagram of a manufacturing step of a sheet-like fibrous structure, FIG. 4 being an explanatory diagram of the sheet-like fibrous structure before stacked, FIG. 5 being an explanatory diagram of a mold, FIG. 6 and FIG. 7 being explanatory diagrams of a manufacturing step of a cushion body, and FIG. 8 being a sectional explanatory diagram of the cushion body.

A seat 1 of the embodiment can be applied to a seat for a vehicle, a train, an airplane or the like, and it may be also applied to various chairs such as a business chair or a care chair. The seat 1 of this embodiment is provided with a seat portion 10 and a seat back portion 20, as shown in FIG. 1. The seat portion 10 and the seat back portion 20 are respectively constituted such that cushion bodies 11 and 21 are placed on seat frames 15 and 25 and the cushion bodies 11 and 21 are coated with covers 13 and 23.

Regarding the cushion body of this embodiment, a forming step (a cushion body forming step) thereof will be explained taking the cushion body 11 of the seat portion 10 as an example. The cushion body 21 is also formed according to a similar method as the above. The cushion body 11 in this embodiment is formed by forming a sheet-like fibrous structure as a fibrous structure where a web 2 has been folded in a standing state (a fibrous structure forming step) described later, cutting this sheet-like fibrous structure into fibrous structure pieces with predetermined shapes to stack a plurality of cut fibrous structure pieces and disposing the plurality of cut fibrous structure pieces in a mold 40 formed with a plurality of steam holes 43 which are ventilation holes on its mold face (a fibrous structure disposing step), and performing high pressure steam molding in high pressure steam molding machine 50 in a state the mold 40 has been clamped (a molding step).

First, the web 2 for forming the cushion body 11 of this embodiment will be explained with reference to FIG. 2 and FIG. 3. The web 2 is one obtained by dispersing and mixing, in matrix fibers composed of assemblies of inelastic crimped short fibers, thermally adhesive composite short fibers having a melting point lower than that of the inelastic crimped short fibers and having a melting point of at least 120° C. as adhesive component.

The web 2 in this embodiment is one obtained by performing cotton blending of inelastic polyester crimped short fibers as the inelastic crimped short fibers and the thermally adhesive composite short fibers composed of thermoplastic elastomer having a melting point lower than a melting point of polyester polymer constituting the inelastic polyester crimped short fibers by 40° C. and inelastic polyester such that the fibers are mainly directed in a longitudinal direction of the web 2. The web 2 of this embodiment has a bulk property of at least 30 kg/m³ and it is formed with cubic fiber crossing points between the thermally adhesive composite short fibers and between the thermally adhesive composite short fibers and the inelastic polyester crimped short fibers.

In this embodiment, hollow polyethylene terephthalate fiber with a single yarn fineness of 12 deniers and a fiber length of 64 mm which have cubic crimp due to anisotropic cooling are used as the inelastic polyester crimped short fibers.

As the inelastic polyester crimped short fibers, short fibers made from ordinary polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polytetramethylene terephthalate, poly-1,4-dimethylcyclohexane terephthalate, polypivalolactone, or copolymer ester thereof, cotton blended material of these fibers, composite fibers composed of two or more kinds of the above polymer components, or the like can be used. Short fibers of polyethylene terephthalate, polytrimethylene terephthalate, or polybutylene terephthalate of these short fibers are desirable. Further, potential crimped fibers composed of two kinds of polyethylene terephthalate and polytrimethylene terephthalate whose inherent viscosities are different from each other or a combination thereof, where crimps have micro-crimps due to heat treatment or the like can also be used.

Further, a sectional shape of the short fiber may be circular, oval, hyterotypic, or hollow. A thickness of this short fiber is in a range of 2 to 200 deniers, especially, preferably in a range of 6 to 100 deniers. Incidentally, when the thickness of the short fiber is small, softness increases, but elasticity of the cushion body often lowers.

Further, when the thickness of the short fiber is excessively thick, handling easiness, especially, formability of the web 2 deteriorates. Furthermore, there is a possibility that the number of constituent fibers decreases excessively, the number of crossing points formed between the short fibers and the thermally adhesive composite short fibers also decreases so that elasticity of the cushion body is hard to develop and simultaneously durability lowers. Furthermore, texture becomes excessively rough and hard.

In the embodiment, as the thermally adhesive composite short fibers, core/sheath type thermally melting composite fibers (a core/sheath ratio=60/40:weight ratio) with a single yarn fineness of 6 deniers and a fiber length of 51 mm which uses thermoplastic polyether ester elastomer with a melting point of 154° C. as sheath component and uses polybutylene terephthalate with a melting point of 230° C. as core component is used.

The thermally adhesive composite short fibers are composed of thermoplastic elastomer and inelastic polyester.

Then, it is preferable that the former occupies at least ½ of a fiber surface. Regarding a weight ratio, it is appropriate that the former and the latter are in a range of 30/70 to 70/30 in a composite ratio. As an aspect of the thermally adhesive composite short fibers may be of a side by side type or of a sheath-core type, but the latter is desirable. In the sheath-core type, the inelastic polyester constitutes the core, but the core may be concentric or eccentric. Especially, the eccentric type is more desirable because coil-like elastic crimps are developed.

As the thermoplastic elastomer, polyurethane elastomer or polyester elastomer is desirable. Especially, the latter is appropriate. As the polyurethane elastomer, polyol with a low melting point having a molar weight of about 500 to 6000, for example, dihydroxy polyether, dihydroxy polyester, dihydroxy polycarbonate, dihydroxy polyester amide, or the like, organic diisocyanate with a molar weight of 500 or less, for example, p, p-diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate hydride, xylylene diisocyanate, 2,6-diisocyanate methyl caproate, hexamethylene diisocyanate, or the like, chain extender with a molar weight of 500 or less, for example, polymer obtained by reaction with glycol, amino alcohol, or triol are used. An especially desirable one of these polymers is polytetramethylene glycol as polyol, or polyurethane using poly-ε-caprolactone or polybutylene adipate. In this case, p,p′-diphenylmethane diisocynate is desirable as organic diisocyanate. Further, p,p′-bidihydroxy-ethoxy benzene and 1,4-butane diol are desirable as the chain extender.

On the other hand, as the polyester elastomer, polyether ester block copolymer obtained by performing copolymerization using thermoplastic polyester as hard segment and using poly (alkylene oxide) glycol as soft segment, more specifically, temary copolymer composed of at least one of dicarboxylic acids selected from aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxy-ethane dicarboxylic acid, or 3-sodium sulfoisophthalic acid, alicyclic dicarboxylic acid such as 1,4-cyclohexane dicarboxylic acid, aliphatic dicarboxylic acid such as succinate, oxalic acid, adipic acid, sebacic acid dodecanedioic acid, dimer acid, ester-forming derivatives thereof, or the like; at least one of diol components selected from aliphatic diol such as 1,4-butane diol, ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, or decamethylene glycol, or alicyclic diol such as 1,1-cyclohexan dimethanol, 1,4-cyclohexan dimethanol, or tricyclodecane dimethanol, ester-forming derivatives thereof, or the like; and at least one of poly (alkylene oxide) glycol such as polyethylene glycol, poly (1,2- and 1,3-propylene oxide) glycol, poly (tetramethylene oxide) glycol, copolymer of ethylene oxide and propylene oxide, copolymer of ethylene oxide and tetrahydrofuran, or the like, where an average molecular weight is in a range of about 400 to 5000 is used.

Considering aspect of adhesiveness with the inelastic polyester crimped short fibers, temperature property, strength, block copolymerization polyether polyester using polybutylene terephthalate as hard segment and using polyoxybutylene glycol as soft segment is desirable. In this case, the polyester component constituting the hard segment includes terephthalic acid as main acid component, and polybutylene terephthalate which is butylene glycol component as main dial component. Of course, a portion (generally, 30 mol % or less) of this acid component may be replaced with other dicarboxylic acid component or oxycarboxylic acid component, and similarly a portion (generally, 30 mol % or less) of glycol component may be replaced with dioxy component other than butylene glycol component.

Further, the polyether portion constituting the soft segment may be polyether replaced with dioxy component other than butylene glycol. Incidentally, various stabilizers, ultraviolet absorbent, thickening branching agent, delusterant, colorant, or other various improvers or the like may be blended in polymer according to necessity.

It is preferable that the degree of polymerization of polyester elastomer is in a range of 0.8 to 1.7 dl/g, especially, in a range of 0.9 to 1.5 dl/g regarding inherent viscosity. If this inherent viscosity is excessively low, a heat adhesion spot formed by the inelastic polyester crimped short fibers constituting the matrix is made breakable. On the other hand, if the inherent viscosity is excessively high, a spindle-shaped node becomes hard to be formed at a heat adhesion time.

As basic characteristics of the thermoplastic elastomer, a fracture elongation is preferably 500% or more, more preferably, 800% or more. If this elongation is excessively low, when the cushion body 11 is compressed and the deformation reaches the heat adhesion point, coupling at this portion becomes breakable.

On the other hand, an elongation stress of 300% of the thermoplastic elastomer is preferably 0.8 kg/mm² or less, more preferably, 0.8 kg/mm². If this stress is excessively large, it becomes hard for the heat-adhesion spot to disperse force applied on the cushion body 11, so that, when the cushion body 11 is compressed, the heat-adhesion spot may be broken by the force applied at that time, or even if it is not broken, the inelastic polyester crimped short fibers constituting the matrix may be also strained or crimps may fatigue.

Further, 300% elongation recovery ratio of thermoplastic elastomer is preferably 60% or more, more preferably, 70% or more. When this elongation recovery ratio is low, even if the cushion body 11 is compressed so that the heat-adhesion spot is deformed, recovery to its original state may become hard. It is required that these thermoplastic elastomers have melting points lower than polymer constituting the inelastic polyester crimped short fibers and they do not cause crimps of the crimped short fibers to thermally fatigue at a hot-melting processing time for forming the heat-adhesion spot. Therefore, the melting point is preferably lower than the melting point of the polymer constituting the short fibers by 40° C. or more, more preferably, by 60° C. or more. Such a melting point of the thermoplastic elastomer can be set to a temperature in a range of 120 to 220° C., for example.

When the difference in melting point is smaller than 40° C., a heat treatment temperature at a melting processing time described later is excessively high, fatigue of crimps of the inelastic polyester crimped short fibers is caused, which results in lowering of mechanical properties of the crimped short fibers. Incidentally, regarding the thermoplastic elastomer, when its melting point can not be observed clearly, a softening point thereof is observed instead of the melting point.

On the other hand, as the inelastic polyester crimped short fibers used as a mating component of the thermoplastic elastomer in the composite fibers, polyester polymers constituting the crimped short fibers forming the matrix, such as described above, are adopted, but polyethylene terephthalate, polymethylene terephthalate, or polybutylene terephthalate is more preferably adopted among them.

The above-described composite fibers are dispersed and blended in a range of 20 to 100%, preferably, 30 to 80% based upon weight of the web 2.

In the web 2 in this embodiment, the thermally adhesive composite short fibers as the binder fibers and the inelastic crimped short fibers as the main fibers are cotton-blended at a weight ratio of 60:40.

When the dispersion and blend ratio of the composite fibers is excessively low, the number of heat-adhesion spots is reduced, so that the cushion body 11 may become easily deformable, or elasticity, repulsive property, and durability may lower. Further, cracks between tops arranged may occur.

In the embodiment, the inelastic polyester crimped short fibers and the thermally adhesive composite short fibers are cotton-blended at the weight ratio of 40:60, and they are formed in the web 2 of coating weight 20 g/m² through a roller card.

The web 2 in this embodiment is formed such that a ratio of fibers oriented in the lengthwise direction of the web is relatively higher than that of fibers oriented in a lateral direction. That is, the web 2 in this embodiment is formed so as to satisfy a relationship of C≧3D/2, preferably, C≧2D per unit volume.

When total numbers of the fibers C oriented in the lengthwise direction (a continuous direction) in this continuous web 2 and the fibers D oriented in the lateral direction (a widthwise direction of the web) are examined. It can be confirmed that C:D=2:1.

Here, as shown in FIG. 2, the fibers oriented in the lengthwise direction of the web 2 are fibers satisfying such a condition that an angle θ of the lengthwise direction of the fibers to the lengthwise direction of the web is in a range of 0°≦θ≦45°, while the fibers oriented in the lateral direction (the widthwise direction of the web) are fibers satisfying such a condition that the angle θ is in a range of 45°<θ≦90°. In the figure, reference symbol a represents fibers constituting the web, reference symbol b represents the lengthwise direction (extending direction) of the web, and reference symbol c represents the fiber direction constituting the web.

Further, regarding the orientation of the fibers constituting the sheet-like fibrous structure, a thickness direction of the sheet-like fibrous structure and a direction extending along a direction perpendicular to a thickness direction thereof means directions within a range of ±45° to these directions.

A direction where each fiber directs can be confirmed by extracting random portions in a surface layer portion and an inner layer portion of the web 2 to observe them using a transmission type optical microscope.

Incidentally, the thickness of the web 2 is 5 mm or more, preferably, 10 mm or more, further preferably 20 mm or more. Generally, the web 2 has a thickness of 5 to 150 mm.

Next, the web 2 formed such that fibers mainly extend along the lengthwise direction is folded like an accordion such that it has a predetermined density and a desired thickness as a structural body, so that cubic fiber crossing points are formed between the composite fibers and between the inelastic polyester crimped short fiber and the composite fibers, and heat treatment is then performed at a temperature (to 80° C.) lower than the melting point of the polyester polymer and higher than the melting point (or a fluidization start point) of the thermoplastic elastomer, so that elastomer component are melt-adhered at the fiber crossing points and flexible heat-adhesion spots are formed.

Specifically, as shown in FIG. 3, the web 2 is folded to an accordion shape by pushing the web 2 into a hot-air suction type heat treatment machine 62 (a length of a heat treatment zone is 5 m and a moving velocity is 1 m/min) by a driving roller 61 with a roller surface velocity of 2.5 m/min and it is formed in a heat-adhered sheet-like fibrous structure with a thickness of 25 mm by treating the web 2 at 190° C. for 5 minutes using Struto equipment (a fibrous structure forming step).

Adhesion spots thermally adhering in a state the thermally adhesive composite short fibers have crossed one another and adhesion spots thermally adhering in a state that the thermally adhesive composite short fibers and the inelastic crimped short fibers have crossed one another are dispersed in the sheet-like fibrous structure thus formed.

It is appropriate for developing cushioning properties, ventilation properties, and elasticity that the density of the sheet-like fibrous structure is in a range of 5 to 200 kg/m³.

By forming the web 2 formed such that their fibers extend along the lengthwise direction in a folding manner, the sheet-like fibrous structure is formed such that the number of fibers oriented in the thickness direction is larger than that of fibers oriented in a direction perpendicular to this thickness direction and a direction of the fibers mainly becomes parallel to the thickness direction. That is, the sheet-like fibrous structure in the embodiment is formed such that when the total number of fibers arranged along in the thickness direction is represented as A and the number of fibers arranged along the direction perpendicular to the thickness direction is represented as B regarding per unit volume, a relationship of A≧3B/2, preferably, A≧2B is satisfied.

Next, the sheet-like fibrous structure is cut in a predetermined shape, and cut pieces are stacked in a vertical direction (a thickness direction T), as shown in FIG. 4. In this embodiment, four kinds of sheet-like fibrous structures 4 a to 4 d of a sheet-like fibrous structure 4 a with a low density, a sheet-like fibrous structure 4 b with a high density, a U-shaped sheet-like fibrous structure 4 c with a U shape for forming a bank portion of the cushion body 11, and a protrusion-shaped sheet-like fibrous structure 4 d for forming a protrusion portion to be slightly protruded between both thighs of a seat occupant are respectively cut in predetermined shapes, the U-shaped sheet-like fibrous structure 4 c and the protrusion-shaped sheet-like fibrous structure 4 d are sandwiched between the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density.

Incidentally, a widthwise direction of the cushion body 11, a lengthwise direction thereof, and a thickness direction thereof are represented as W, L, and T in FIG. 4, respectively.

In this embodiment, the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density having a density higher than that of the sheet-like fibrous structure 4 a with a low density are stacked. It is preferable that the fiber density of the sheet-like fibrous structure 4 a with a low density is in a range of 10 to 20 kg/m³ and the fiber density of the sheet-like fibrous structure 4 b with a high density is in a range of 20 to 35 kg/m³ before thermal molding.

Incidentally, the sheet-like fibrous structure 4 a with a low density corresponds to the first fibrous structure of the present invention while the sheet-like fibrous structure 4 b with a high density corresponds to the second fibrous structure thereof.

As described above, the sheet-like fibrous structure 4 a with a low density is formed of a sheet-like fibrous structure obtained by folding the web 2 obtained by blending the main fibers and the binder fibers in a standing state. The sheet-like fibrous structure 4 a with a low density is arranged on a side (an upper side on FIG. 4) of a sitting surface 10 a of the seat 1, and it serves to receive load from a body of a seat occupant directly or indirectly via a cover.

The sheet-like fibrous structure 4 b with a high density is formed of a sheet-like fibrous structure made from substantially the same fiber material as that of the sheet-like fibrous structure 4 a with a low density. The sheet-like fibrous structure 4 b with a high density is arranged on the side (a lower side on FIG. 4) of the seat frame 15 of the seat 1. The sheet-like fibrous structure 4 b with a high density is placed on an upper face with the sheet-like fibrous structure 4 a with a low density to serve to support the same.

These sheet-like fibrous structures 4 a to 4 d are stacked in their thickness direction T. That is, stacking is performed such that a direction of fibers extends in a vertical direction.

Further, holt-melt films, hot-melt unwoven cloths, hot-melt adhesives, or the like are arranged at portions where the sheet-like fibrous structures 4 a to 4 d abut on one another according to necessity.

The sheet-like fibrous structures 4 a to 4 d thus stacked are arranged in a mold 40 such as shown in FIG. 5 and compressed (a fibrous structure arranging step). The mold 40 of this embodiment is composed of a first mold 41 and a second mold 42. The first mold 41 is a mold used to form a shape of the cushion body 11 positioned on the side of the sitting surface 10 a (namely, a surface), while the second mold 42 is a mold used to form a shape of the cushion body 11 positioned on the side of the seat frame 15, namely, on the side of a back surface 10 b (a non-load receiving face).

When the first mold 41 and the second mold 42 are fastened, a cavity 40 a having a desired undulation shape of the cushion body 11 is formed. Further, steam holes 43 are formed on a portion or a whole of a mold face of the mold 40. In the embodiment, the steam holes are hardly formed on the first mold 41 while a plurality of steam holes 43 are bored over a whole face of the second mold 42 in the second mold 42.

The mold 40 can be formed using such metal as iron, steel, aluminum, glass fiber, or carbon fiber, or it may be formed of any synthetic resin.

FIG. 6 is a sectional view of a state that the sheet-like fibrous structures 4 a to 4 d have been disposed in the mold 40 and the mold 40 has been fastened. The sheet-like fibrous structures 4 a to 4 d are formed to be larger than the cavity 40 a of the mold 40 in a natural state by about 1.2 to 3.0 times in volume. Accordingly, the sheet-like fibrous structures 4 a to 4 d are changed to a state that they have been compressed to the shape of the cavity 40 a at a mold fastening time.

The sheet-like fibrous structure 4 a with a low density is received in the cavity 40 a such that an upper face thereof abuts on an inner wall face of the first mold 41. Further, the sheet-like fibrous structure 4 b with a high density is arranged in the cavity 40 a such that a lower face thereof abuts on an inner wall portion of the second mold 42.

Next, as shown in FIG. 7, the mold 40 in which the sheet-like fibrous structures 4 a to 4 d have been disposed is entered into a high pressure steam molding machine 50. A steam introducing port (not shown) is formed on an upper portion of the high pressure steam molding machine 50, so that high pressure steam can be introduced from the outside of the high pressure steam molding machine 50 into the high pressure steam molding machine 50.

The mold 40 is installed in the high pressure steam molding machine 50 such that the second mold 42 is directed vertically upwardly and the first mold 41 is directed vertically downwardly. After steam is blown to the mold 40, cooling and mold-releasing are performed to obtain a cushion body 11 (cooling and mold-releasing step).

In the molding step of this embodiment, a temperature inside the high pressure steam molding machine 50 is controlled such that steam with a molding temperature can be blown to the molding 40.

Here, the molding temperature is a temperature higher than a melting point of the thermally adhesive composite short fibers serving as the binder fibers, namely, higher than a melting point of thermoplastic elastomer, and lower than a melting point of matrix fibers (the inelastic crimped short fibers) serving as the main fibers.

In order to raise a temperature of steam to the molding temperature, a temperature inside the high pressure steam molding machine 50 is first raised to the molding temperature by a heater (not shown) and a pressure inside the high pressure steam molding machine 50 is raised from an ambient atmospheric pressure (about 1 atm) to at least saturated steam pressure of steam or higher in the molding temperature.

In this embodiment, since the melting point of the binder fibers is about 154° C., the molding temperature is set to 161° C. higher than the melting point. In this embodiment, then, since water vapor (H₂O) serving as heat conduction material is blown to the mold 40, the temperature inside the high pressure steam molding machine 50 is raised up to the molding temperature of 161° C. in about 30 seconds and the pressure inside the high pressure steam molding machine 50 is raised to atmospheric pressure of about 5.5 atm (about 0.557 MPa) which is a boiling point at the molding temperature of 161° C. That is, the saturated steam pressure at the molding temperature of 161° C. is about 5.5 atm.

In the molding step, water vapor with the molding temperature is blown to the mold 40 in a state that the temperature and the pressure inside the high pressure steam molding machine 50 have been kept in the molding temperature and a predetermined pressure. In this embodiment, molding is performed by blowing steam to the mold 40 for about one minute and 10 seconds.

Thereafter, the temperature inside the high pressure steam molding machine 50 is lowered to the molding temperature or lower in about one minute and the pressure inside the high pressure steam molding machine 50 is reduced to an ambient atmospheric pressure. Then, the mold 40 is taken out of the high pressure steam molding machine 50 to be cooled (a cooling step), and the cushion body 11 thermally molded is released from the mold 40 (a mold-releasing step).

In this embodiment, tact time for thermally molding the cushion body 11 in the high pressure steam molding machine 50 can be set to about 3 to 5 minutes.

By blowing steam with the molding temperature to the mold in this manner, steam enters in the sheet-like fibrous structures 4 a to 4 d having ventilation properties from steam holes 43 of the mold 40, and it exits from other steam holes 43 to the outside of the mold 40. The sheet-like fibrous structures 4 a to 4 d are disposed in the mold 40 in their compressed state, and crossing points between the thermally adhesive composite short fibers and between the thermally adhesive composite short fibers and the inelastic crimped short fibers are caused to thermally adhere to one another due to steam heat so that the cushion body is formed in the shape of the cavity 40 a of the mold 40.

Further, hot-melt films, hot-melt unwoven clothes, hot-melt adhesives, or the like disposed among the sheet-like fibrous structures 4 a to 4 d are melted due to steam heat and the sheet-like fibrous structures 4 a to 4 d are fixed to one another.

Thus, fibers in the sheet-like fibrous structures 4 a to 4 d are caused to thermally adhere to one another due to steam and the sheet-like fibrous structures 4 a to 4 d are fixed to one another by the hot-melt film, a hot-melt unwoven cloth, hot-melt adhesive, or the like, so that a cushion body 11 with a predetermined shape is formed. Incidentally, dish cloth may be inserted on a surface according to necessity, or wires made from steel or the like may be inserted among the sheet-like fibrous structures 4 a to 4 d.

When steam with the molding temperature is blown to the mold 40 inside the high pressure steam molding machine 50 raised up to the saturated steam pressure like this embodiment, a molding time can be reduced largely. That is, since steam with the molding temperature has a thermal capacity larger than that of hot air, the binder fibers can be melted in a short time.

Incidentally, when high pressure steam is blown to the mold under atmospheric pressure, since the high pressure steam adiabatically expands immediately and a temperature of the steam lowers, it is difficult to cause steam with the molding temperature to reach inside of the fiber bodies. Therefore, a long molding time is required notwithstanding.

Further, in this embodiment, by shortening the molding time largely, a time when fibers are exposed to heat is shortened so that texture of the cushion body 11 molded is made excellent.

In the cushion body 11 in this embodiment, the sheet-like fibrous structures 4 a to 4 d where the directions of fibers are oriented in the thickness direction T are stacked and the high pressure steam molding is performed. Accordingly, the fibers constituting the cushion body 11 are arranged along a direction in which load acts when a seat occupant sits on the seat 1. With such a constitution, the cushion body 11 in this embodiment has ventilation properties and can secure a proper hardness to a stress direction, and it provides dispersibility of stress and excellent durability.

Further, the cushion body 11 in this embodiment is molded in a state that it has been compressed by the mold 40, and it can take a three-dimensional and complicated undulation shape so as to conform with the shape of the cavity 40 a of the mold 40. At this time, cushioning feeling can be adjusted partially according to a compression degree in the mold 40.

The mold 40 in this embodiment is arranged such that the second mold 42 is oriented vertically upwardly, namely, to the side of the steam introducing port. Further, formation is made such that the steam holes 43 of the second mold 42 outnumbers the steam holes 43 of the first mold 41. Therefore, an amount of steam introduced from the steam holes 43 of the second mold 42 into the cavity 40 a is more than the amount of steam introduced from the steam holes 43 of the first mold 41.

The steam introduced from the steam holes 43 of the second mold 42 is exhausted from the inside of the cavity 40 a through the steam holes formed on a side face of the second mold 42 or the steam holes formed on a side face of the first mold 41. A flow of this steam is indicated by dotted arrows in FIG. 7.

Incidentally, in the mold 40 of this embodiment, any steam hole is not formed in a region of the first mold 41 corresponding to the sitting surface 10 a. Thereby, it is made possible to reduce the hardness of the sitting surface 10 a to provide soft touch feeling to a seat occupant, as described later.

In this embodiment, since the amount of steam introduced from the second mold 42 is more than the amount of steam introduced from the first mold 41, a heat amount supplied to the sheet-like fibrous structure 4 b with a high density disposed on the side of the second mold 42 is more than a heat amount supplied to the sheet-like fibrous structure 4 a with a low density disposed on the side of the first mold 41. When the heat amount to be supplied is much, fibers are melted in a short time by the thermal molding and many fibers are fixed due to heat adhesion so that hardness becomes high.

Further, since the sheet-like fibrous structure 4 b with a high density has a high fiber density where fibers come in close contact with one another, the number of fibers fixed by thermal molding is increased as compared with a fibrous structure with a low fiber density, which results in increase of hardness.

On the other hand, steam holes are hardly formed in the first mold 41 at all, and especially, any steam hole is not formed on a region corresponding to the sitting surface. Therefore, the heat amount supplied to the sheet-like fibrous structure 4 a with a low density is low, and especially, temperature rising in a region corresponding to the sitting surface becomes very slow. Thus, since the number of fibers fixed by the heat adhesion is reduced in the sheet-like fibrous structure 4 a with a low density, hardness becomes low.

Further, since the fiber density is low and intervals among fibers are formed to be coarse in the sheet-like fibrous structure 4 a with a low density, the number of fibers fixed by the thermal molding is reduced as compared with a fibrous structure with a high fiber density, so that hardness becomes low.

Therefore, since the sheet-like fibrous structure 4 a with a low density becomes lower in surface layer hardness than the sheet-like fibrous structure 4 b with a high density, a flexing degree of the former in the thickness direction T to a load due to sitting of a seat occupant becomes large.

On the other hand, since the sheet-like fibrous structure 4 b with a high density becomes higher in hardness than the sheet-like fibrous structure 4 a with a low density, durability to weight in the thickness direction T due to sitting can be improved.

Accordingly, a cushion body 11 including both soft touch feeling during sitting and durability to load due to sitting can be provided.

FIG. 8 is a sectional view of a cushion body 11 released from the mold. FIG. 8 shows a sectional shape obtained by cutting the cushion body 11 of the seat 1 shown in FIG. 1 along a direction of arrow line A-A′.

As shown in this figure, the cushion body 11 in this embodiment is one thermally molded in a state that the sheet-like fibrous structure 4 a with a low density, the sheet-like fibrous structure 4 b with a high density, the U-shaped sheet-like fibrous structure 4 c with a U shape for forming a bank portion of the cushion body 11, and the protrusion-shaped sheet-like fibrous structure 4 d for forming a protrusion portion to be slightly protruded between both thighs of a seat occupant have been stacked in the thickness direction T.

Hot-melt films, hot-melt unwoven cloths, hot-melt adhesives, or the like are disposed at portions where the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density abut on each other, where the sheet-like fibrous structure 4 a with a low density and the U-shaped sheet-like fibrous structure 4 c abut on each other, where the sheet-like fibrous structure 4 a with a low density and the protrusion-shaped sheet-like fibrous structure 4 d abut on each other, the sheet-like fibrous structure 4 b with a high density and the U-shaped sheet-like fibrous structure 4 c abut on each other, and where the sheet-like fibrous structure 4 b with a high density and the protrusion-shaped sheet-like fibrous structure 4 d abut on each other, so that these fibrous structures are bonded to one another.

The sheet-like fibrous structure 4 b with a high density is formed to have a fiber density higher than that of the sheet-like fibrous structure 4 a with a low density. In this embodiment, the fiber density of the sheet-like fibrous structure 4 a with a low density after thermally molded is in a range of about 10 to 20 kg/m³, while the fiber density of the sheet-like fibrous structure 4 b with a high density after thermally molded is in a range of about 20 to 35 kg/m³.

In the cushion body 11 in this embodiment, thus, the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density are stacked, and the sheet-like fibrous structure 4 a with a low density having a low fiber density is disposed on the side of the sitting surface 10 a.

Here, since a case that the fiber density is low means a structure where the number of gaps among fibers is large, the flexing degree of the sheet-like fibrous structure in the thickness direction T thereof to load is large. On the contrary, since a case that the fiber density is high means that the number of gaps among fibers is small, and the fibers come in close contact with one another, the flexing degree of the sheet-like fibrous structure in the thickness direction T thereof to load is small.

Incidentally, in the text, that the flexing degree is large means that a degree of deformation of the fibrous structure in a load direction to applied load is large, and specifically it includes both that a compression ratio of compression of the fibrous structure in the load direction to load is large and that a degree of bending of the fibrous structure in the load direction is large.

On the contrary, that the flexing degree is small means that the degree of deformation of the fibrous structure in the load direction to applied load is small, and specifically it includes both that the compression ratio of compression of the fibrous structure in the load direction to load is small and that the degree of bending of the fibrous structure in the load direction to load is small.

By disposing the sheet-like fibrous structure 4 a with a low density whose flexing amount to load acting in the thickness direction T is arranged on the side of the sitting surface 10 a, the sheet-like fibrous structure 4 a with a low density receives load from the body of seat occupant to flex sufficiently largely in the thickness direction T thereof (arrow F1 in FIG. 8). Accordingly, the cushion body 11 of this embodiment can provide soft touch feeling to a seat occupant during sitting.

Further, since the flexing amount to load acting in the thickness direction T is small in the sheet-like fibrous structure 4 b with a high density supporting the sheet-like fibrous structure 4 a with a low density (arrow F2 in FIG. 8), the sheet-like fibrous structure 4 b with a high density is hard to fatigue in the load direction, so that durability of the cushion body 11 can be secured.

It is preferable that the sheet-like fibrous structure 4 a with a low density is formed such that its fiber density is lower than that of the sheet-like fibrous structure 4 b with a high density by about 5 to 25 kg/m³.

When a difference in fiber density is smaller than 5 kg/m³, a flexing amount of the sheet-like fibrous structure 4 b with a high density becomes excessively large and no proper hardness can be obtained so that it becomes difficult to maintain the durability of the cushion body 11. On the contrary, when the difference in fiber density is larger than 25 kg/m³, hardness of the whole cushion body 11 excessively increases, so that soft touch feeling on the surface is lost.

The U-shaped sheet-like fibrous structure 4 c is disposed between the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density. The U-shaped sheet-like fibrous structure 4 c in this embodiment is formed from approximately the same material as that for the sheet-like fibrous structure 4 a with a low density or the sheet-like fibrous structure 4 b with a high density.

Further, the protrusion-shaped sheet-like fibrous structure 4 d is similarly disposed between the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density. The protrusion-shaped sheet-like fibrous structure 4 d is also formed from approximately the same material as that for the sheet-like fibrous structure 4 a with a low density or the sheet-like fibrous structure 4 b with a high density.

Incidentally, in the cushion body 11 in this embodiment, the bank portion and the protrusion portion are formed using the U-shaped sheet-like fibrous structure 4 c and the protrusion-shaped sheet-like fibrous structure 4 d, but the bank portion or the protrusion portion may be formed utilizing the shape of the cavity 40 a without using these sheet-like fibrous structures.

Further, all of the sheet-like fibrous structure 4 a with a low density, the sheet-like fibrous structure 4 b with a high density, the U-shaped sheet-like fibrous structure 4 c, and the protrusion-shaped sheet-like fibrous structure 4 d are formed from the same fiber material. Therefore, when the cushion body 11 is discarded due to damage of the cushion body 11 or duration of life, separation thereof can be saved, so that recycling easiness is skipped.

Incidentally, in this embodiment, the example that one sheet-like fibrous structure 4 a with a low density and one sheet-like fibrous structure 4 b with a high density have been stacked as the cushion body 11 is shown, but regarding each of the fibrous structures, the number of stacks may be plural. In this case, it is preferable that the number of fibrous structures to be stacked is adjusted according to feeling, durability, a size, or the like required for the cushion body 11.

For example, when it is desired to improve feeling of the sitting surface 10 a, two or more sheet-like fibrous structures 4 a with a low density are stacked. On the contrary, when it is desired to further improve the durability of the cushion body 11, two or more sheet-like fibrous structures 4 b with a high density are stacked.

Thus, by increasing/decreasing the number of the fibrous structures to be stacked, a cushion body 11 with desired feeling or durability can be provided.

Further, since there is not any difference between the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density except for the difference in fiber density, it is difficult to discriminate them from each other based upon their appearances. Therefore, there is a possibility that when they are disposed in the mold 40 at a manufacturing time the cushion body 11, the mold 40 is assembled in a state that the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density are put in the mold 40 at their erroneous arrangement positions. In this case, the sheet-like fibrous structure 4 b with a high density having a high fiber density is disposed on the side of sitting surface 10 a, so that it becomes difficult to provide a cushion body with soft touch feeling.

Therefore, the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density are colored differently. By making colors different, confirmation and discrimination with eyes is made easy, so that a predetermined sheet-like fibrous structure can be disposed at a predetermined position reliably at the assembling time.

In order to color the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density differently, for example, there is such means that the inelastic crimped short fibers or the thermally adhesive composite short fibers of raw materials is added with pigment. By adding pigment in this manner, the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density can be colored differently.

As the pigment added in the short fibers, various chromatic color pigments, black pigment, and the like used for dyeing of fibers are used. As the material for pigment, there are inorganic material and organic material.

As examples of the chromatic color pigment, there are titanium yellow, yellow iron oxide, chrome yellow, red oxide of iron, blue verditer, iron blue pigment, cobalt blue, aluminum powder, copper powder, silver powder, gold powder, zinc powder, barytes powder, pigment yellow, molybdate orange, permanent yellow, permanent red, balkan first red, balkan first orange, first violet, first scarlet, phthlocyanine green, indanthrene blue, and the like.

As examples of the black pigment, there are carbon black, graphite, iron black, talc, and the like.

As examples of the white pigment, there are zinc oxide, titanium dioxide, and the like.

These pigments can dye the fibrous structure wholly or partially according to blending thereof at the time of manufacturing the web 2.

At a time pigments being blended into the short fibers, a surface of the pigment may be preliminarily treated using various surface treatment agents. As these surface treatment agents, for example, silane coupling agent, titanium coupling agent, zirconium coupling agent, aluminum coupling agent, or the like can be used.

It is preferable that the content of pigment in a fibrous structure is in a range of about 0.01 to 10 weight %. When the content is less than 0.01 weight %, coloration of the fibrous structure is poor, so that it becomes difficult to confirm or discriminate kinds of fibrous structures with eyes. On the other hand, when the content is more than 10 weight %, such a drawback arises that agglomeration of pigment occurs, the structure of the fibrous structure becomes brittle, or pigment is eluted to adhere on a cover during thermal molding due to an excessive amount of the pigment.

Both of the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density may be colored, and either one thereof may be colored. Further, the sheet-like fibrous structures may be colored as a whole, and only viewable portions thereof may be colored.

In the above embodiment, though the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density can be discriminated by coloring them differently, but the both may be discriminated by attaching pattern different from each other at viewable positions of both or one of the sheet-like fibrous structure 4 a with a low density and the sheet-like fibrous structure 4 b with a high density.

Though the cushion body 11 has been explained above, a cushion body 21 for the seat back portion may be similarly formed. Regarding the cushion body 21, a direction in which load acts when a seat occupant sits is a thickness direction of the cushion 21. Accordingly, in order to secure dispersibility of hardness or stress and durability in a stress direction, a three-dimensional shape can be achieved by stacking sheet-like fibrous structures in a direction in which stress acts and performing high pressure steam forming within the mold 40. Then, a seat 1 is formed by arranging the cushion bodies 11 and 21 thus formed on the sheet frames 15 and 25 and coating them with covers 13 and 23 (an assembling step).

Incidentally, when the cushion body 11 is formed, the cover 13, and the sheet-like fibrous structures 4 a to 4 d are stacked via hot-melt films, hot-melt unwoven clothes, hot-melt adhesives, or the like, and they are disposed in the mold 40, so that high pressure steam forming may be performed. Thereby, the cover 13 can be formed integrally with the cushion body 11. The cover 23 may be similarly handled.

If the high pressure steam molding is performed in a state that the sheet-like fibrous structures 4 a to 4 d are coated with the cover 13, the sheet-like fibrous structures 4 a to 4 d and the cover 13 are arranged in the mold 40, when the molding temperature is excessively high, the cover 13 may lose color. In this case, therefore, the molding temperature may be set to be lower than the melting temperature of dye dyeing the cover 13.

Further, in the above embodiment, water vapor is blown to the mold 40, but the present invention is not limited to this treatment and heat conducting material which does not adversely affect fibers can be used. That is, steam of the selected heat conducting material can be blown to the mold 40 by raising pressure in the high pressure steam molding machine 50 such that a desired temperature is a boiling point of the selected heat conducting material.

Further, in the embodiment, the cushion body 11 is formed using the sheet-like fibrous structures 4 a to 4 d formed by folding the web 2 in an accordion shape as the fibrous structures, but the present invention is not limited to this constitution, and a fibrous structure obtained by stacking many webs 2 in the thickness direction can be used as the fibrous structure, or a raw fiber assembly obtained by dispersing and blending main fibers and binder fibers may be used.

Furthermore, in the embodiment, the cushion bodies 11 and 21 obtained by stacking the sheet-like fibrous structures 4 a to 4 d to perform the high pressure steam forming are used for the seat portion 10 and the seat back portion 20, but the present invention is not limited to this constitution, and a cushion body obtained by stacking sheet-like fibrous structures 4 a to 4 d to perform high pressure steam forming may be used at a portion on which load due to seat occupant sitting acts such as an arm rest or a head rest.

Next, details of a seat using the cushion body 11 will be explained. FIG. 9 is sectional views showing a state that a seat portion of a seat has been cut in a widthwise direction, FIG. 9 (a) being a view showing the whole of the seat portion, and FIG. 9 (b) being a view showing a region circled in FIG. 9 (a) in an enlarged manner.

As shown in FIG. 9 (a), the seat portion 10 includes a cushion body 11, a cover 13, and a seat frame 15. As shown in FIG. 9 (b), a surface of the cushion body 11 is coated with the cover 13, and a trim cord 17 made from resin is sewn to an end portion of the cover 13. The trim cord 17 is formed to have an about J shape in section, and a member such as a string can be hooked on a bent portion formed at a distal end of the trim cord 17.

On the other hand, an engagement portion 19 is provided inside the seat frame 15 in a projecting manner. A wire is provided on the side of a distal end of the engagement portion 19. The cover 13 can be fixed to the seat frame 15 by hooking the bent portion of the trim cord 17 on the wire of the engagement portion 19.

Next, a method for manufacturing a seat portion 10 of a seat for a vehicle will be explained in detail.

First, a hot-melt film is caused to adhere to a surface of the cushion body 11 before the high pressure steam forming, and the surface is coated with the cover 13. Next, the cushion body 11 whose surface is coated with the cover 13 is introduced into a high pressure steam molding machine, wherein high pressure steam molding is performed so that the cushion body 11 and the cover 13 are formed integrally.

The molded cushion body 11 is taken out of the high pressure steam molding machine, and it is left for a while to be dried. After dried, the trim cord 17 made from resin is sewn on the end portion of the cover 13. Next, winkles of a surface of the seat portion 10 are removed by pulling the end portion of the cover 13 and the trim cord 17 is hooked to the engagement portion 19.

The above is directed to explanation about the seat portion 10 of the seat 1, but the seat back portion 20 can also be manufactured according to similar steps. 

1. A cushion body obtained by molding a fibrous structure obtained by mixing main fibers and binder fibers using a mold having a cavity with a predetermined shape, wherein the cushion body is formed by stacking a plurality of the fibrous structures, the plurality of the fibrous structures stacked includes a first fibrous structure and a second fibrous structure which is smaller in flexing degree to load in a thickness direction than the first fibrous structure, the first fibrous structure is disposed nearer a load receiving face of the cushion body on which external load is applied than the second fibrous structure.
 2. The cushion body according to claim 1, wherein the first fibrous structure is formed from approximately the same fiber material as the second fibrous structure and is formed to have a fiber density lower than that of the second fibrous structure.
 3. The cushion body according to claim 2, wherein the first fibrous structure has a fiber density of 10 to 20 kg/m³ and the second fibrous structure has a fiber density of 20 to 35 kg/m³.
 4. The cushion body according to claim 1, wherein the first fibrous structure and the second fibrous structure are applied with different colors or patterns regarding appearances thereof so that both the fibrous structures can be discriminated from each other.
 5. The cushion body according to claim 1, wherein the cushion body is molded by blowing steam to the fibrous structure through steam holes formed on a mold face of the mold under barometrical pressure higher than atmospheric pressure.
 6. The cushion body according to claim 5, wherein the barometrical pressure is a saturated steam pressure at a temperature at a melting point of the binder fibers or above and lower than a melting point of the main fibers.
 7. The cushion body according to claim 1, wherein the steam holes are formed to be more in a region corresponding to the side of a non-load receiving face where the second fibrous structure is disposed than in a region corresponding to the load receiving face in the mold, and steam is blown to the fibrous structure through the steam holes on the side of the non-load receiving face.
 8. A seat including a cushion body and a seat frame supporting the cushion body, wherein the cushion body is either one of the cushion bodies according to claim
 1. 9. A method of manufacturing a cushion body comprising a fibrous structure, comprising at least: a fibrous structure forming step of successively folding a web composed of main fibers and binder fibers for each predetermined length to form a fibrous structure as a stacked state; a fibrous structure disposing step of disposing a first fibrous structure of the first fibrous structure and a second fibrous structure included in the fibrous structure nearer a load receiving face of the cushion body than the second fibrous structure and disposing the first and second fibrous structures in a mold having a cavity with a predetermined shape in a stacked and compressed state of the first and second fibrous structures, where the second fibrous structure is smaller in flexing degree to load in a thickness direction than the first fibrous structure; and a molding step of thermally molding the fibrous structure in the mold to form a cushion body.
 10. The method of manufacturing a cushion body according to claim 9, wherein, in the molding step steam is blown to the fibrous structure through steam holes formed on a mold face of the mold under barometrical pressure higher than atmospheric pressure.
 11. The method of manufacturing a cushion body according to claim 10, wherein the barometrical pressure is a saturated steam pressure at a temperature a melting point of the binder fibers or above and lower than a melting point of the main fibers.
 12. The method of manufacturing a cushion body according to claim 9, wherein the steam holes formed to be more in a region corresponding to the side of a non-load receiving face where the second fibrous structure is disposed than in a region corresponding to the load receiving face in the mold, and steam is blown to the fibrous structure through the steam holes on the side of the non-load receiving face in the molding step.
 13. A method of manufacturing a seat comprising a cushion body and a seat frame supporting the cushion body, comprising at least: a step of forming the cushion body according to the method of manufacturing a cushion body according to claim 9, and a step of attaching the cushion body to the seat frame.
 14. A seat including a cushion body and a seat frame supporting the cushion body, wherein the cushion body is either one of the cushion bodies according to claim
 2. 15. A seat including a cushion body and a seat frame supporting the cushion body, wherein the cushion body is either one of the cushion bodies according to claim
 3. 16. A seat including a cushion body and a seat frame supporting the cushion body, wherein the cushion body is either one of the cushion bodies according to claim
 4. 17. A seat including a cushion body and a seat frame supporting the cushion body, wherein the cushion body is either one of the cushion bodies according to claim
 5. 18. A seat including a cushion body and a seat frame supporting the cushion body, wherein the cushion body is either one of the cushion bodies according to claim
 6. 19. A seat including a cushion body and a seat frame supporting the cushion body, wherein the cushion body is either one of the cushion bodies according to claim
 7. 20. A method of manufacturing a seat comprising a cushion body and a seat frame supporting the cushion body, comprising at least: a step of forming the cushion body according to the method of manufacturing a cushion body according to claim 10; and a step of attaching the cushion body to the seat frame.
 21. A method of manufacturing a seat comprising a cushion body and a seat frame supporting the cushion body, comprising at least: a step of forming the cushion body according to the method of manufacturing a cushion body according to claim 11; and a step of attaching the cushion body to the seat frame.
 22. A method of manufacturing a seat comprising a cushion body and a seat frame supporting the cushion body, comprising at least: a step of forming the cushion body according to the method of manufacturing a cushion body according to claim 12; and a step of attaching the cushion body to the seat frame. 